The present invention relates to a for a marine engine and more particularly to a stage carburetor for introduction of an air-fuel mixture into the crankcase of a two stroke marine engine.
Prior art marine engine carburetors utilize a single bore or throat with a pivoting throttle plate for delivering an air-fuel mixture to a reed block for introduction of the mixture into the crankcase of a two stroke marine engine. The cross-sectional area of the throttle bore had to be of a size sufficient to provide an adequate air-fuel mixture during a wide open throttle operation of the engine. However, the rather large throttle bore resulted in poor fuel economy at low R.P.M.'s or idle operation of the engine and also caused poor operation quality at idle and low R.P.M. The large throttle bore also caused fuel puddling during operation at idle speeds due to the low velocity of the air-fuel mixture and resulting poor atomization of the fuel.
It is an object of the present invention to provide a two stage carburetor which will have a primary throttle bore that introduces an air-fuel mixture into the crankcase at low engine R.P.M.'s or during idle operation and a secondary throttle bore that becomes operable at higher R.P.M. engine operation.
Such a two stage carburetor ensures a high velocity of the air-fuel mixture through the reed blocks regardless of the throttle setting of the engine.
It is a further object of the present invention to eliminate fuel puddling and provide better low speed fuel economy and engine running quality for low R.P.M. operation of the engine, while still maintaining high power during wide open throttle operation of the engine.